//
// Copyright (c) 2004-2024 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// * Neither the name of Jaroslaw Kowalski nor the names of its
//   contributors may be used to endorse or promote products derived from this
//   software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
//

namespace NLog.LayoutRenderers
{
    using System.Text;
    using NLog.Config;
    using NLog.Layouts;

    /// <summary>
    /// Render a NLog Configuration variable assigned from API or loaded from config-file
    /// </summary>
    /// <remarks>
    /// <a href="https://github.com/NLog/NLog/wiki/Var-Layout-Renderer">See NLog Wiki</a>
    /// </remarks>
    /// <seealso href="https://github.com/NLog/NLog/wiki/Var-Layout-Renderer">Documentation on NLog Wiki</seealso>
    [LayoutRenderer("var")]
    public class VariableLayoutRenderer : LayoutRenderer
    {
        /// <summary>
        /// Gets or sets the name of the NLog variable.
        /// </summary>
        /// <docgen category='Layout Options' order='10' />
        [RequiredParameter]
        [DefaultParameter]
        public string Name { get; set; }

        /// <summary>
        /// Gets or sets the default value to be used when the variable is not set.
        /// </summary>
        /// <remarks>Not used if Name is <c>null</c></remarks>
        /// <docgen category='Layout Options' order='10' />
        public string Default { get; set; }

        /// <summary>
        /// Gets the configuration variable layout matching the configured Name
        /// </summary>
        /// <remarks>Mostly relevant for the scanning of active NLog Layouts (Ex. CallSite capture)</remarks>
        public Layout ActiveLayout => TryGetLayout(out var layout) ? layout : null;

        /// <inheritdoc/>
        protected override void InitializeLayoutRenderer()
        {
            if (TryGetLayout(out var layout) && layout != null)
            {
                //pass loggingConfiguration to layout
                layout.Initialize(LoggingConfiguration);
            }

            base.InitializeLayoutRenderer();
        }

        /// <summary>
        /// Try lookup the configuration variable layout matching the configured Name
        /// </summary>
        private bool TryGetLayout(out Layout layout)
        {
            layout = null;
            //Note: don't use LogManager (locking, recursion)
            return Name != null && LoggingConfiguration?.TryLookupDynamicVariable(Name, out layout) == true;
        }

        /// <inheritdoc/>
        protected override void Append(StringBuilder builder, LogEventInfo logEvent)
        {
            if (Name != null)
            {
                if (TryGetLayout(out var layout))
                {
                    //ignore NULL, but it set, so don't use default.
                    layout?.Render(logEvent, builder);
                }
                else if (Default != null)
                {
                    //fallback
                    builder.Append(Default);
                }
            }
        }
    }
}


